The Arsenal manager, Arsène Wenger, believes Per Mertesacker has improved with every Premier League appearance. Photograph: Julian Finney/Getty Images

Despite a prevailing view that Per Mertesacker is too ponderous to operate at the top level of English football he is in the throes of emerging as Arsenal's new Tony Adams, according to Arsène Wenger.

As he prepared his team to face Sunderland on Sunday, the Frenchman also offered a counterintuitive view of a defence that has allowed opposition players to pour through it to collect 16 league goals already this season. Still bedding in together, the Arsenal manager sees in them the foundations of a new, long-term rearguard.

Of the 6ft 6in German central defender, who was signed from Werder Bremen on deadline day for £8m, Wenger said: "Mertesacker is getting better every game. Yes, he has said to me it is [more] quick here, relentless. He adapts quite well, he is getting more aggressive. I like him personally. I think he is a very intelligent player. Trust the Germans, they can fight."

Asked if he had compared him with Adams, the club legend who captained Arsenal to four league titles and two Doubles, Wenger said: "Yes, a little bit like that. Not the quickest but he uses his brains. He is 26 with 74 Germany caps [he was recently 27]."

Overcoming a start that has seen Arsenal win only two of their seven outings is the challenge as the campaign moves into the long autumn and winter months. Wenger believes the criticism Mertesacker has attracted is a consequence of the side's poor form. "If you don't win then nobody's good. It is like that. The players are mentally strong, and I think he is and will get over that. I am happy from what I see from him," he added, before joking about Mertesacker's height. "I think people are a bit shocked – 'well, he's too tall for Arsenal' – because they are used for us to be a bit short."

Mertesacker will also emerge as the vocal leader of the defensive pack. "We have had more quieter defences recently but I think Mertesacker can be a talker," the manager said. "He will come out of himself more, don't worry."

Wenger points to having to choose Alex Song alongside Mertesacker on occasion due to injuries, with Thomas Vermaelen and Bacary Sagna now long-term absentees from what would be the first-choice defence. "Song is a centre-back with class but he's not what you call a centre-back who talks and wants to play there. He does it for the team."

When Sagna, who is 28, Mertesacker, 27, Vermaelen, 25, and Kieran Gibbs, 22, are all fit Wenger sees a potentially immovable base that has been absent from the club since the disbanding of the 2004 Invincibles' first-choice defence of Lauren, Kolo Touré, Sol Campbell and Ashley Cole. "I hope they can grow over a series of seasons. For us that is what is at stake," Wenger says.

If Arsenal can secure three points against Steve Bruce's side then Wednesday's trip to Marseille for the Champions League group game becomes easier. After a draw at Borussia Dortmund and a win over Olympiakos at the Emirates, Wenger stated that the two matches with the French club will determine their fortunes in the group stage. "The games against Marseille will decide our qualification, it's as simple as that. If we take four points we will qualify."

Despite discussing the loss of Cesc Fábregas to Barcelona and Samir Nasri to Manchester City in the summer, and the need to rebuild, Wenger will not be drawn on whether a finish outside the top four and the Champions League reckoning would be a disappointment.

Asked if qualification for the Europa League next year would be a disaster, he said: "We are not as far as that. After seven games you cannot say that is out of reach [qualification for the Champions League]. Let's not talk too much and focus on our games and get stability in our results."